[SolAndLuna]

If you have an Arcane weapon equipped in your main hand, and a non-Arcane weapon in your off hand, for some reason the Spelledge ability applies to both weapons instead of just one, thus using the stronger of the two, even if it isn't actually enchanted with Arcane.
If the Arcane weapon is in the off hand, however, everything works as normal, only using the Arcane weapon as a casting tool.

For example, I have these weapons equipped. The first description is Glacies Anima (Regalia'd Spine Leash), the second description is Eisjaeger (Regalia'd Fenri). To clarify, both weapons are made out of Dragon Remains, and I'm testing this with a Grimalkin.









So long as these weapons are exactly in this order, Eisjaeger gets used as a casting tool, despite very definitely not being a Spelledge weapon:


If I swap the weapons around, however, Glacies Anima is used as the casting tool instead.